U.S. patent application number 10/422816 was filed with the patent office on 2004-02-12 for combustion condition detection apparatus for an internal combustion engine.
This patent application is currently assigned to MITSUBISHI DENKI KABUSHIKI KAISHA. Invention is credited to Dohi, Masakazu, Sera, Yoshiyuki, Takahashi, Yasuhiro, Uchida, Toshio.
Application Number | 20040025570 10/422816 |
Document ID | / |
Family ID | 31492270 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040025570 |
Kind Code |
A1 |
Dohi, Masakazu ; et
al. |
February 12, 2004 |
Combustion condition detection apparatus for an internal combustion
engine
Abstract
A combustion condition detecting apparatus for an internal
combustion engine has a current distributor that distributes an ion
current, a band pass filter which extracts a knock vibration
component from a current distributor output, a knock determination
section which outputs a knock pulse if the extracted knock
vibration component is larger than a knock detection threshold
value, a combustion determination section which outputs a
combustion pulse when an current distributor output is larger than
a combustion pulse threshold value, an ignition signal
determination section which makes a determination on the basis of
an ignition signal as to whether energization of an ignition coil
for ignition in another cylinder is started, and an ion current
limiting section which limits its ion current output to the current
distributor during a predetermined time period after the start of
energization of the ignition coil for ignition in the another
cylinder.
Inventors: |
Dohi, Masakazu; (Hyogo,
JP) ; Uchida, Toshio; (Hyogo, JP) ; Sera,
Yoshiyuki; (Tokyo, JP) ; Takahashi, Yasuhiro;
(Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
MITSUBISHI DENKI KABUSHIKI
KAISHA
|
Family ID: |
31492270 |
Appl. No.: |
10/422816 |
Filed: |
April 25, 2003 |
Current U.S.
Class: |
73/35.08 |
Current CPC
Class: |
G01L 23/225 20130101;
G01L 23/221 20130101 |
Class at
Publication: |
73/35.08 |
International
Class: |
G01L 023/22 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2002 |
JP |
2002-228837 |
Claims
What is claimed is:
1. A combustion condition detecting apparatus for an internal
combustion engine, comprising: an ignition coil for generating a
high voltage for ignition on the basis of an ignition signal; an
ignition plug which makes a spark to ignite a fuel-air mixture when
the high voltage for ignition of the ignition coil is applied
thereto; and an ion current detector which detects an ion current
generated in a combustion chamber in the internal combustion engine
immediately after ignition, extracts a knock vibration component
from the detected ion current, outputs a knock pulse when the knock
vibration component is larger than a knock detection threshold
value, and inhibits detection of the ion current while a false ion
current is being generated.
2. An apparatus according to claim 1, wherein the ion current
detector includes: a current distributor which distributes the ion
current; a band pass filter which extracts the knock vibration
component from an output from the current distributor; knock
determination means of outputting the knock pulse if the extracted
knock vibration component is larger than the knock detection
threshold value; combustion determination means of outputting a
combustion pulse when an output from the current distributor is
larger than a combustion pulse threshold value; ignition signal
determination means of making a determination on the basis of the
ignition signal as to whether energization of the ignition coil for
ignition in another cylinder is started; and ion current limiting
means provided in front of the current distributor, the ion current
limiting means limiting the output of the ion current to the
current distributor during a predetermined time period after the
start of energization of the ignition coil for ignition in the
another cylinder.
3. An apparatus according to claim 2, wherein the ion current
limiting means measures the predetermined time after the start of
energization of the ignition coil for ignition in the another
cylinder by timer means, and stops supply of the ion current to the
current distributor while measuring the predetermined time
period.
4. An apparatus according to claim 2, wherein the ion current
limiting means makes a digital link between ion current data at the
start of energization of the ignition coil for ignition in the
another cylinder and ion current data after a lapse of the
predetermined time period from the start of energization of the
ignition coil for ignition in the another cylinder, and outputs the
data.
5. An apparatus according to claim 3, wherein the ion current
limiting means limits the output of the ion current to the current
distributor during the predetermined time period after the start of
energization of the ignition coil for ignition in the another
cylinder.
6. A combustion condition detecting apparatus for an internal
combustion engine, comprising: an ignition coil for generating a
high voltage for ignition on the basis of an ignition signal; an
ignition plug which makes a spark to ignite a fuel-air mixture when
the high voltage for ignition of the ignition coil is applied
thereto; and an ion current detector which detects an ion current
generated in a combustion chamber in the internal combustion engine
immediately after ignition, extracts a knock vibration component
from the detected ion current, outputs a knock pulse when the knock
vibration component is larger than a knock detection threshold
value, and inhibits detection of the knock vibration component
while a false ion current is being generated.
7. An apparatus according to claim 6, wherein the ion current
detector includes: a current distributor which distributes the ion
current; a band pass filter which extracts the knock vibration
component from an output from the current distributor; knock
determination means of outputting the knock pulse if the extracted
knock vibration component is larger than the knock detection
threshold value; combustion determination means of outputting a
combustion pulse when an output from the current distributor is
larger than a combustion pulse threshold value; ignition signal
determination means of making a determination on the basis of the
ignition signal as to whether energization of the ignition coil for
ignition in another cylinder is started; and knock detection
inhibition means inserted between the band pass filter and the
knock determination means, the knock detection inhibition means
inhibiting the output of the knock vibration component to the knock
determination means during a predetermined time period after the
start of energization of the ignition coil for ignition in the
another cylinder.
8. An apparatus according to claim 7, wherein the knock detection
inhibition means measures the predetermined time after the start of
energization of the ignition coil for ignition in the another
cylinder by timer means, and stops supply of the knock vibration
component to the knock determination means while measuring the
predetermined time period.
9. An apparatus according to claim 7, wherein the knock detection
inhibition means inhibits the output of the knock vibration
component to the knock determination means during a time period
after the start of energization of the ignition coil for ignition
in the another cylinder, the time period being determined by
actually measuring the knock vibration component generated by the
false ion current.
10. An apparatus according to claim 8, wherein the knock detection
inhibition means inhibits the output of the knock vibration
component to the knock determination means during the predetermined
time period after the start of energization of the ignition coil
for ignition in the another cylinder.
11. An apparatus according to claim 4, wherein the ion current
limiting means limits the output of the ion current to the current
distributor during the predetermined time period after the start of
energization of the ignition coil for ignition in the another
cylinder.
12. An apparatus according to claim 9, wherein the knock detection
inhibition means inhibits the output of the knock vibration
component to the knock determination means during the predetermined
time period after the start of energization of the ignition coil
for ignition in the another cylinder.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a combustion condition
detection apparatus for an internal combustion engine for sensing
at least the occurrence of a misfire or a knock in an internal
combustion engine by detecting a change in the amount of ions
generated by combustion in the internal combustion engine.
[0003] 2. Description of the Related Art
[0004] It is generally known that ions are generated when a fuel is
combusted in a cylinder of an internal combustion engine. If a
probe to which a high voltage is applied is placed in the cylinder,
the generated ions can be observed as an ion current.
[0005] When a knock occurs in the internal combustion engine, a
vibration component due to the knock is superimposed on the ion
current. Therefore it is possible to detect the occurrence of a
knock by extracting such a vibration component.
[0006] A conventional knock detection apparatus will be described
with reference to drawings. FIG. 9 is a diagram showing the
structure of a conventional combustion condition detecting
apparatus for an internal combustion engine by using ion current,
e.g., the one disclosed in Japanese Patent Laid-Open No.
2001-140740. FIG. 10 is a diagram showing details of the structure
of an ion current detector in the conventional combustion condition
detecting apparatus for an internal combustion engine. FIG. 11 is a
timing chart for explaining the operation of the conventional knock
detection apparatus.
[0007] Referring to FIG. 9, an ignition plug 1 is used as a probe
for detecting an ion current. A bias means 3 is charged at a high
voltage (bias voltage) for detection of ion current by using a
secondary voltage of an ignition coil 2. After the completion of
discharge for ignition, the bias voltage of charge accumulated in
the bias means 3 during the discharge period is applied to the
terminal of the ignition plug 1 to enable an ion current to be
detected by an ion current detector 4 connected to an engine
control unit (ECU) 5.
[0008] Referring to FIG. 10, when ion current 3s is input by the
high voltage applied by the bias means 3, it is distributed by a
current distributor 6 in the ion current detector 4 to a band pass
filter (BPF) 7 for extracting a knock vibration component and a
comparison section 8 for determination of a combusting condition.
This comparison section 8 determines that combustion is being
effected and outputs a pulse to the ECU 5 if the input is larger
than a predetermined combustion pulse threshold value 8a. From this
pulse, a combusting/misfiring condition can be determined. This
pulse will hereinafter be referred to as combustion pulse 8s.
[0009] A knock vibration component is extracted by the BPF 7 and
then amplified by an amplifier 9. A comparison section 10 for
determination of a knock determines that there is a knock if the
vibration component is larger than a predetermined knock detection
threshold value 10a, and then an output section 11 outputs a knock
pulse 11s to the ECU 5.
[0010] Japanese Patent Laid-Open No. 2001-073862 discloses a knock
detection apparatus which has an integration circuit for
integrating (charging) a vibration component superimposed on an ion
current, and a discharge circuit for discharging a predetermined
amount of charge from the charge obtained as a result of the
integration (charging), and which autonomously adjusts a knock
detection threshold value according to discharge balance between
the integration circuit and the discharge circuit.
[0011] Further, Japanese Patent Laid-Open No. 10-077944 discloses a
knock detection apparatus described below. FIG. 12 is a diagram
showing the structure of another conventional knock detection
apparatus disclosed in Japanese Patent Laid-Open No. 10-077944.
[0012] When a knock occurs in an internal combustion engine, a
knock signal at a particular frequency is superimposed on an ion
current in a decreasing period after the ion current has peaked. As
means for detecting a knock through ion current, therefore, a
method of detecting only such a knock signal at a particular
frequency while removing other signals (e.g., an LC resonance
waveform) is preferably used. Therefore, it is preferable to
provide a knocking window which is opened at a time after a time
when unnecessary signals disappear and which is closed at a
suitable time after a decrease in ion current (for example, at
ATDC60.degree.), and to detect a knock on the basis of an output
from an ion current detection section during a time period through
which the knocking window is open.
[0013] A "knocking detection method using ion current" has already
been proposed (see JP 06-159129 A) in which a knock signal is
separated from an output signal from this ion current detection
section by using a band pass filter and is integrated and a knock
is detected on the basis of the integrated value.
[0014] Referring to FIG. 12, an LC resonance waveform is removed
from an output from an ion current detection section 19 by an LC
resonance mask section 20 and the output from the ion current
detection section 19 is thereafter input to a processing section 23
via a band pass filter section 21 and a peak hold (or integration)
section 22. The operation of the peak hold section 22 is controlled
through an window which is opened following a predetermined time
after ignition according to the rotational speed of the internal
combustion engine and the load on the internal combustion engine,
and which is closed at a closing time corresponding to about
50.degree. CA in terms of crank angle after opening. Noise
components are removed by utilizing a phenomenon in which an
integral value of noise assumed to be an instantaneous change in
ion concentration increases in a stepping manner and a phenomenon
in which an integral value of a knock signal increases
continuously. It is well known that the LC resonance mask section
20 is provided between the ion current detection section 19 and the
band pass filter section 21 for the purpose of eliminating the
influence of LC resonance after discharge.
[0015] In the above-mentioned conventional knock detection
apparatus disclosed in Japanese Patent Laid-Open No. 2001-140740,
when energization of the ignition coil for ignition in another or
the next cylinder is started, a false ion current 3sa is generated
by electromagnetic induction caused by the start of energization of
the ignition coil for ignition in the another or next cylinder, as
shown in (c) of FIG. 11. False ion current 3sa appears as if
combustion is effected or a knock occurs in the cylinder
corresponding to the ignition coil through which ion current
detection is being performed. A false knock component signal 9sa is
generated as a knock component signal 9s by false ion current 3sa,
as shown in (e) of FIG. 11. At this time, an erroneous knock pulse
11sa is generated as a knock pulse 11s, as shown in (f) of FIG. 11.
Also, an erroneous combustion pulse 8sa is generated as a
combustion pulse 8s, as shown in (d) of FIG. 11. Thus, there has
been a problem in that there is a fear of erroneous combustion
determination or erroneous knock determination.
[0016] The method of autonomously adjusting a knock detection
threshold value according to discharge balance between an
integration circuit and a discharge circuit has a problem in that
even when no knock occurs, there is a fear of charging with a knock
component signal generated by a false ion current, which increases
the threshold value for detection of knocks, resulting in detection
failure.
[0017] Further, the method of separating a knock signal from an
output signal from the ion current detection section 19 by using
the band pass filter section 21, integrating (holding the peak of)
the separated knock signal, and detecting a knock on the basis of
the integral (held peak) value has a problem in that a knock
component signal generated by a false ion current cannot be removed
by the band pass filter section 21, it is, therefore, impossible to
discriminate the knock component signal generated by the false ion
current and a knock from each other with reliability, and there is
a fear of occurrence of a detection result erroneously indicating a
knock.
SUMMARY OF THE INVENTION
[0018] In view of the above-mentioned problems, an object of the
present invention is to provide a combustion condition detection
apparatus for an internal combustion engine capable of preventing
erroneous combustion determination and erroneous knock
determination and effectively improving the detection accuracy.
[0019] According to the present invention, a combustion condition
detecting apparatus for an internal combustion engine includes an
ignition coil, an ignition plug, and an ion current detector. The
ignition coil generates a high voltage for ignition on the basis of
an ignition signal, and the ignition plug makes a spark to ignite a
fuel-air mixture when the high voltage for ignition of the ignition
coil is applied thereto. Further, the ion current detector detects
an ion current generated in a combustion chamber in the internal
combustion engine immediately after ignition, and extracts a knock
vibration component from the detected ion current. In addition, the
ion current detector outputs a knock pulse when the knock vibration
component is larger than a knock detection threshold value, and
inhibits detection of the ion current while a false ion current is
being generated. As a result, there is obtained such an effect that
erroneous combustion determination and erroneous knock
determination can be avoided, thereby being capable of greatly
improving the detection accuracy.
[0020] Further, in another embodiment mode of the present
invention, a combustion condition detecting apparatus for an
internal combustion engine includes an ignition coil, an ignition
plug, and an ion current detector. The ignition coil generates a
high voltage for ignition on the basis of an ignition signal, and
the ignition plug makes a spark to ignite a fuel-air mixture when
the high voltage for ignition of the ignition coil is applied
thereto. In addition, the ion current detector detects an ion
current generated in a combustion chamber in the internal
combustion engine immediately after ignition, extracts a knock
vibration component from the detected ion current, outputs a knock
pulse when the knock vibration component is larger than a knock
detection threshold value, and inhibits detection of the knock
vibration component while a false ion current is being generated.
As a result, there is obtained such an effect that erroneous knock
determination can be avoided, thereby being capable of greatly
improving the detection accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In the accompanying drawings:
[0022] FIG. 1 is a diagram showing the structure of an ion current
detector in a combustion condition detection apparatus for an
internal combustion engine in Embodiment 1 of the present
invention;
[0023] FIG. 2 is a timing chart showing the operation of the ion
current detector in Embodiment 1 of the present invention;
[0024] FIG. 3 is a flowchart showing the operation of the ion
current detector in Embodiment 1 of the present invention;
[0025] FIG. 4 is a diagram showing the structure of an ion current
detector in a combustion condition detection apparatus for an
internal combustion engine in Embodiment 2 of the present
invention;
[0026] FIG. 5 is a timing chart showing the operation of the ion
current detector in Embodiment 2 of the present invention;
[0027] FIG. 6 is a flowchart showing the operation of the ion
current detector in Embodiment 2 of the present invention;
[0028] FIG. 7 is a diagram showing the structure of an ion current
detector in a combustion condition detection apparatus for an
internal combustion engine in Embodiment 4 of the present
invention;
[0029] FIG. 8 is a timing chart showing the operation of the ion
current detector in Embodiment 4 of the present invention;
[0030] FIG. 9 is a diagram showing the structure of a conventional
combustion condition detection apparatus for an internal combustion
engine;
[0031] FIG. 10 is a diagram showing the structure of an ion current
detector in the conventional combustion condition detection
apparatus for the internal combustion engine;
[0032] FIG. 11 is a timing chart showing the operation of the
conventional ion current detector; and
[0033] FIG. 12 is a diagram showing the structure of another
conventional ion current detector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
[0034] A combustion condition detection apparatus for an internal
combustion engine in accordance with Embodiment 1 of the present
invention will be described with reference to the drawings. FIG. 1
is a diagram showing the structure of an ion current detector in
Embodiment 1 of the present invention. Components other than the
ion current detector are the same as those in the above-mentioned
example of conventional art. In each of Embodiments described
below, the difference from the conventional art also resides only
in the ion current detector. In the drawings, the same reference
symbols indicate identical or corresponding portions.
[0035] Referring to FIG. 1, the ion current detector has an ion
current limiting means 16, a timer means 16a, ignition signal
determination means 12 to 15, a current distributor 6, a BPF 7, a
comparison section 8 for determination of a combusting condition, a
combustion pulse threshold value 8a, an amplifier 9, a knock
determination means 17, and an output section 11. The knock
determination means 17 is the same as the knock determination
comparison section 10 shown in FIG. 10, i.e., the section in which
the existence of a knock is determined if the vibration component
of the knock component signal is larger than the predetermined
knock detection threshold value 10a. The comparison section 8 for
determination of a combusting condition and the combustion pulse
threshold value 8a constitute a combustion determination means.
[0036] The operation of the combustion condition detection
apparatus for the internal combustion engine in Embodiment 1 of the
present invention will now be described with reference to the
drawings.
[0037] FIG. 2 is a timing chart showing the operation of the ion
current detector in Embodiment 1 of the present invention. FIG. 3
is a flowchart showing the operation of the ion current detector in
Embodiment 1 of the present invention.
[0038] The description will be made of ion current detection from
one of a plurality of cylinders (four cylinders). The detection
from each of the other cylinders (second to fourth cylinders) is
performed in the same manner as that from the first cylinder.
[0039] A false ion current 3sa is generated by electromagnetic
induction caused when energization of the ignition coil in another
of the other cylinders (second to fourth cylinders) is started, as
shown in (c) of FIG. 2. A false knock component signal 9sa is
generated as a knock component signal 9s by false ion current 3sa,
as shown in (e) of FIG. 2. At this time, an erroneous knock pulse
11sa is generated as a knock pulse 11s, as shown in (f) of FIG. 2.
Also, an erroneous combustion pulse 8sa is generated as a
combustion pulse 8s, as shown in (d) of FIG. 2.
[0040] The ion current is limited by the ion current limiting means
16 so that the ion current is as shown in (g) of FIG. 2 and the
combustion pulse is as shown in (h) of FIG. 2. After the
limitation, no false ion current is detected.
[0041] The knock component signal is made as shown in (i) of FIG.
2. Also, as a result of the limitation of the ion current, the
knock pulses are formed only of normal knock pulses, as shown in
(j) of FIG. 2. That is, the ion current limiting means 16 limits
the combustion pulses 8s and knock pulses 11s obtained as a
combustion detection result.
[0042] The operation will be described in detail with reference to
the flowchart of FIG. 3.
[0043] In step 101, detection of ion current is performed by the
ion current limiting means 16. If there is no ion current,
detection of ion current is performed again, if there is an ion
current, the process advances to step 102.
[0044] In steps 102 to 104, determination is made by ignition
signal determination means 13 to 15 as to whether energization of
one of the ignition coils 2 to 4 is started. If energization of any
of the ignition coils 2 to 4 is not started, the process advances
to step 105. If energization of one of the ignition coils 2 to 4 is
started, the process advances to step 106.
[0045] In step 105, the ion current is output from the ion current
limiting means 16 to the current distributor 6. The current
distributor 6 outputs currents to the BPF 7 and the comparison
section for determination of a combusting condition.
[0046] On the other hand, in step 106, determination is made by the
timer means 16a in the ion current limiting means 16 as to whether
the present time is within a predetermined time period from the
start of energization in the another of the other cylinders.
[0047] If the present time is not within the predetermined time
period, that is, the predetermined time period has passed, the ion
current is output to the current distributor 6 by the ion current
limiting means 16 in step 105. If the present time is within the
predetermined time period, waiting to the end of the predetermined
time period after the start of energization in the another of the
other cylinders is performed by the timer means 16a in the ion
current limiting means 16. By this waiting, the supply of ion
current to the current distributor 6 is stopped.
[0048] Since the detection of ion current is limited and since the
supply of ion current to the current distributor 6 is stopped, no
false ion current is generated, as shown in (g) of FIG. 2, and only
normal combustion pulses result, as shown in (j) of FIG. 2.
[0049] Since the supply of ion current to the current distributor 6
is stopped for a predetermined period of time, no false ion current
is generated, as shown in (g) of FIG. 2, and only knock pulses
result, as shown in (j) of FIG. 2.
[0050] Further, a method may be used in which the ion current
limiting means 16 converts the ion current into digital data and a
digital link is made between the data on the ignition coil in the
another cylinder at the start of energization and the data on the
another cylinder after a lapse of the predetermined time period
from the start of energization. Reconversion of the data to an
analog signal may be made, for example, by current distributor 6 or
the like at a suitable point in a following stage.
[0051] As described above, when energization of the ignition coil
for ignition in another of the cylinders is started, a false ion
current is generated by electromagnetic induction caused by the
start of energization of the ignition coil for ignition in the
another cylinder as if combustion is effected or a knock occurs in
the cylinder corresponding to the ignition coil through which ion
current detection is being performed. According to Embodiment 1 of
the present invention, the ion current output and the knock
component signal output are limited to prevent output of such false
ion current and such false knock component signal, thereby avoiding
erroneous combustion determination or erroneous knock determination
to greatly improve the detection accuracy.
Embodiment 2
[0052] A combustion condition detection apparatus for an internal
combustion engine in accordance with Embodiment 2 of the present
invention will be described with reference to the drawings. FIG. 4
is a diagram showing the structure of an ion current detector in
Embodiment 2 of the present invention.
[0053] Referring to FIG. 4, the ion current detector has ignition
signal determination means 12 to 15, a current distributor 6, a BPF
7, a comparison section 8 for determination of a combusting
condition, a combustion pulse threshold value 8a, an amplifier 9, a
knock detection inhibition means 18, a timer means 18a, a knock
determination means 17, and an output section 11. The knock
determination means 17 is the same as the knock determination
comparison section 10 shown in FIG. 10, i.e., the section in which
the existence of a knock is determined if the vibration component
of the knock component signal is larger than the predetermined
knock detection threshold value 10a. The comparison section 8 for
determination of a combusting condition and the combustion pulse
threshold value 8a constitute a combustion determination means.
[0054] The operation of the combustion condition detection
apparatus for the internal combustion engine in Embodiment 2 of the
present invention will now be described with reference to the
drawings.
[0055] FIG. 5 is a timing chart showing the operation of the ion
current detector in Embodiment 2 of the present invention. Further,
FIG. 6 is a flowchart showing the operation of the ion current
detector in Embodiment 2 of the present invention.
[0056] When energization of the ignition coil in another of the
other cylinders is started, a false ion current 3sa is generated by
electromagnetic induction, as shown in (c) of FIG. 5. A knock
component signal 9sa is generated by false ion current 3sa in a
knock component signal 9s which is extracted by the BPF 7 from one
of ion currents distributed by the current distributor 6 and is
amplified by the amplifier 9, as shown in (d) of FIG. 5. If this
knock component signal 9sa is used for knock detection, an
erroneous knock pulse 11sa is generated, as shown in (e) of FIG.
5.
[0057] Detection of the knock component signal is inhibited by the
knock detection inhibition means 18 so that the knock component
signal is as shown in (f) of FIG. 5, no erroneous knock pulse 11sa
such as shown in (e) of FIG. 5 is generated, and only normal knock
pulses result, as shown in (g) of FIG. 5.
[0058] The operation will be described in detail with reference to
the flowchart of FIG. 6.
[0059] In step 201, when an ion current is input, a determination
is made by the knock detection inhibition means 18 as to whether a
knock component signal exists. If it is determined that no pulse
exist as knock component signal, a determination is again made as
to whether a knock component signal pulse exists. If a knock
component signal exists, the process advances to step 202.
[0060] Next, in steps 202 to 204, determination is made by ignition
signal determination means 13 to 15 as to whether energization of
one of the ignition coils 2 to 4 in the another cylinder is
started. If energization of any of the ignition coils 2 to 4 in the
another cylinder is not started, the process advances to step 205.
If energization of one of the ignition coils 2 to 4 in the another
cylinder is started, the process advances to step 206.
[0061] Next, in step 205, the knock component signal is output from
the knock detection inhibition means 18 to the knock determination
means 17.
[0062] On the other hand, in step 206, determination is made by the
knock detection inhibition means 18 as to whether the present time
is within a predetermined time period from the start of
energization in the another of the other cylinders. This
predetermined time period is determined by actually measuring the
knock component signal 9sa generated by false ion current, as shown
in (d) of FIG. 5.
[0063] If the present time is not within the predetermined time
period, that is, the predetermined time period has passed, the
knock component signal is output to the knock determination means
17 by the knock detection inhibition means 18 in step 205. If the
present time is within the predetermined time period, detection of
the knock component signal is inhibited during the time period
corresponding to the first pulse after the start of energization in
the another cylinder by the knock detection inhibition means
18.
[0064] Since the knock component signal is not supplied to the
knock determination means 17 by the knock detection inhibition
means 18 during the predetermined time period, knock determination
is not made and no false knock component signal is generated, as
shown in (f) of FIG. 5, and only normal knock pulses result, as
shown in (g) of FIG. 5.
[0065] While the predetermined time period is set as described
above, it is desirable that the predetermined time period be
extended to the end of vibration if noise vibration does not end by
one wave.
[0066] A method may also be used in which detection of the knock
component signal during the predetermined time period after a start
of energization of the ignition coil is inhibited by timer means
18a in the knock detection inhibition means 18 to achieve the same
effect.
[0067] As described above, when energization of the ignition coil
for ignition in another of the cylinders is started, a false ion
current is generated by electromagnetic induction caused by the
start of energization of the ignition coil for ignition in the
another cylinder as if combustion is effected or a knock occurs in
the cylinder corresponding to the ignition coil through which ion
current detection is being performed. According to Embodiment 2 of
the present invention, output of the knock component signal is
inhibited to prevent output of such false knock component signal,
thereby avoiding erroneous knock determination to greatly improve
the detection accuracy.
Embodiment 3
[0068] While Embodiments 1 and 2 have been described with respect
to a start of energization of the ignition coil for ignition in
another of the other cylinders, the above-mentioned operation may
be limited to a start of energization of the ignition coil for
ignition in the next cylinder.
[0069] As described above, when energization of the ignition coil
for ignition in another of the cylinders is started, a false ion
current is generated by electromagnetic induction caused by the
start of energization of the ignition coil for ignition in the
another cylinder as if combustion is effected or a knock occurs in
the cylinder corresponding to the ignition coil through which ion
current detection is being performed. According to Embodiment 3 of
the present invention, the ion current output and the knock
component signal output are limited to prevent output of such false
ion current and such false knock component signal, thereby avoiding
erroneous combustion determination or erroneous knock determination
to greatly improve the detection accuracy.
Embodiment 4
[0070] A combustion condition detection apparatus for an internal
combustion engine in accordance with Embodiment 4 of the present
invention will be described with reference to the drawings. FIG. 7
is a diagram showing the structure of an ion current detector in
Embodiment 4 of the present invention.
[0071] Referring to FIG. 7, the ion current detector has a current
distributor 6, a BPF 7, a comparison section 8 for determination of
a combusting condition, a combustion pulse threshold value 8a, an
amplifier 9, a knock determination comparison section 10, and an
output section 11. Further, the ion current detector has ignition
signal determination means 12 to 15, an ion current limiting means
16 having a timer means 16a, and a knock detection inhibition means
18 having a timer means 18. The comparison section 8 for
determination of a combusting condition and the combustion pulse
threshold value 8a constitute a combustion determination means.
[0072] The operation of the combustion condition detection
apparatus for the internal combustion engine in Embodiment 4 of the
present invention will now be described with reference to the
drawings.
[0073] FIG. 8 is a timing chart showing the operation of the ion
current detector in Embodiment 4 of the present invention.
[0074] When energization of the ignition coil in another of the
other cylinders is started, a false ion current 3sa is generated by
electromagnetic induction, as shown in (c) of FIG. 8. A knock
component signal 9sa is generated by false ion current 3sa in a
knock component signal 9s which is extracted by the BPF 7 from one
of ion currents distributed by the current distributor 6 and is
amplified by the amplifier 9, as shown in (d) of FIG. 8. A
threshold value Th1A determined according to charge-discharge
balance is increased (Th1aA) by charging with this knock component
signal, as shown in (d) of FIG. 8. With this increase, a knock
detection threshold value Th2B determined by a function of the
threshold value Th1A is also increased (Th2aB), as shown in (d) of
FIG. 8.
[0075] In this situation, knock pulses 11s are formed as shown in
(e) of FIG. 8. If a knock component signal such as shown in (f) of
FIG. 8 is generated as a result of the increase in threshold value
Th1A and the increase in threshold value Th2B caused by false knock
component signal 9sa, threshold values Th1A and threshold values
Th2B become as shown in (f) of FIG. 8. Then, the knock component
signal is not detected and knock pulses 11s are formed as shown in
(g) of FIG. 8. That is, there is a fear of failure to detect a
knock, which should essentially be detected.
[0076] Therefore, as in the above-mentioned Embodiment 1 or 2,
detection of false ion current 3sa or false knock component signal
9sa is avoided by using the ion current limiting means 16 or the
knock detection inhibition means 18. In this case, the knock
component signal becomes as shown in (h) of FIG. 8, the threshold
value Th1A is not increased by charging with false knock component
signal 9sa, and the threshold value Th2B is also as shown in (h) of
FIG. 8. Knock pulses such as shown in (i) of FIG. 8 result.
[0077] The threshold value Th1A and the threshold value Th2B are
not increased by false knock component signal 9sa, so that, even
when a knock component signal such as shown in (j) of FIG. 8 is
thereafter generated, the threshold value Th1A and the threshold
value Th2B are as shown in (j) of FIG. 8 and the knock component
signal is detected. Knock pulses obtained in this case are as shown
in (k) of FIG. 8.
* * * * *